Buying a used Dodge Challenger can be tricky--as sporty muscle cars, there's always a concern the car was driven harder than an ordinary commuter vehicle. If you'd rather have a V-6 than a V-8 for gas mileage reasons, look at 2011 or newer models, as the upgraded 3.6-liter V-6 is a significant step up from the previous 250-horsepower, 3.5-liter engine. Performance fiends will find both 6.1-liter and 6.4-liter HEMI engines to be fun and fast, but the larger engine will be more expensive, as it wasn't offered until 2011.